1. Field of the Invention
This invention relates to an automatic system for performing in situ a process of low temperature chemical vapor deposition of high purity metals.
2. Description of Related Art
There is need for a system for depositing CVD copper metallurgy on semiconductor wafers. This requirement is coupled with the limitations and problems of present technology of metallurgy in semiconductor chip wiring, interlevel connection (studs), electromigration, and circuit speed.
A currently available commercial metal sputter deposition system employs a specially designed reaction/deposition chamber on a sputter system as a manufacturing type system to replace aluminum-copper and other metals with pure copper by using chemical vapor deposition (CVD) as the transport mechanism to fill via holes, wiring lines, and interconnection studs.
Existing approaches to the present metallurgy and delivery systems are: to vary the copper percentage in the aluminum-copper; the use of barriers to stop electromigration; the use of other metals such as tungsten for studs; the use of evaporation, PIB (Partially Ionized Beam), ECR (Electron Cyclotron Resonance), and sputtering to fill the same topography. At present there appears to a need for a system to deposit CVD copper. However it is known how to deposit tungsten by CVD techniques. The system for copper is very different in design of equipment and process technology.
The Beach et al U. S. patent application Ser. No. 68,695 filed Jun. 30, 1987 and United Kingdom Application Number 88109444.5, published in the United Kingdom as Publication No. 0 297 348 published Jan. 4, 1989 for "Method for Chemical Vapor Deposition of Copper, Silver and Gold Using a Cyclopentadienyl Metal Complex" describes using CVD deposition of copper to form semiconductor chip metallization using thermal CVD (with a thermal reactor.) The, reactor heats a precursor compound carrying the copper causing the compound to dissociate leaving the copper metal behind, to deposit on the substrate. A simple reactor is shown with the substrate 24 suspended above the compound 30 which sublimes.
The steps outlined in the Beach et al application are as follows:
a) a vacuum of 0.001 Torr is applied to the chamber carrying the substrate to clean the reactor, PA0 b) the pressure is raised to 0.1 Torr. PA0 c) the external walls of reactor 10 are heated to about 70.degree. C. while the reactor can be evacuated by a trapped diffusion pump. PA0 d) the substrate is heated to about 150.degree.-220.degree. C. PA0 e) the compound 30 sublimes and vapors rise to the substrate where the gaseous precursor decomposes depositing metal upon the substrate.
In example I in Beach et al, a water ice bath is placed about the reactor in FIG. 1 of Beach et al, initially. Then the substrate holder is heated to 215.degree. C. and the ice bath is replaced by the 70.degree. C. bath, yielding a copper deposit almost immediately upon a substrate of silicon with a Cr adhesion film on the surface.
Patents which relate to CVD reactors and metal have been found, as follows:
U.S. Pat. No. 4,388,342 of Suzuki et al for a method for CVD describes supplying an auxiliary gas which contains the gaseous compound into the reaction chamber to compensate for the consumed gaseous compound in the reaction chamber in response to the measurement of the concentration of the gaseous compound; U.S. Pat. No. 4,503,807 by Nakayama et al for CVD apparatus describes loading chamber and reactor; separate-automatic cassette loading; U.S. Pat. No. 4,636,401 of Yamazaki et al describes an energy and gas flow system; U.S. Pat. No. 4,607,591 of Spitz for a CVD heater control circuit--describes temperature sensor for control of wafer heater by feedback; U.S. Pat. No. 4,596,208 by Wolfson et al for a CVD reaction chamber--describes a reaction chamber and thermocouple for reading temperature.